[2] It is part of the C. trilobus aggregate, whose members are characterized by a funnel or dish-shaped labellum and an often heart or kidney-shaped solitary leaf.

[1] Corybas hypogaeus is a terrestrial, perennial herb with a solitary reniform (kidney-shaped) to cordiform (heart-shaped) leaf born on a petiole 10–15 mm long.

The dorsal sepal is narrow at the base and broad towards the rounded tip; it is light green often with purple flecks running down the middle.

Its main portion is strongly cupped, and its tip is markedly laciniate (deeply jagged).

[3] Corybas hypogaeus can be distinguished from other members of the C. trilobus aggregate by its the diminutive flower, which is commonly buried in leaf litter, and its characteristically jagged, cupped labellum.

[3] It is highly similar to the recently described species C. sanctigeorgianus, from which it can be distinguished by its labellum with a green-tinted center, rather than creamy white, and its dorsal sepal equal to the length to the labellum or slightly longer (rather than noticeably longer).